The need for an appropriate balance of crude fiber in the diet of mammalian organisms has been recognized. For many years nutritionists have noted the crude fiber content of foods and the need for this fiber in a balanced diet. However, crude fiber is only part of what is generally referred to as "dietary fiber". In a general sense dietary fiber can be thought of as the undigestible portion of the foods we eat. A more precise definition is that it consists of the parts of plant cells that are not easily broken-up by the digestive enzymes of man. Specifically, dietary fiber may be defined as the sum of the polysaccharides and lignin which are not digested by the endogenous secretions of the human gastrointestinal tract. Thus, dietary fiber is not a single substance but it is composed of at least five different and complex materials including lignin, cellulose, hemicelluloses, pectins, gums and mucilages.
The individual components of dietary fiber may be conveniently divided into two major groups, soluble dietary fiber and insoluble dietary fiber. Insoluble dietary fiber is made up of lignin, cellulose and hemicelluloses. Soluble dietary fibers are substances like pectins, gums and mucilages as well as some hemicelluloses which are not "fibrous" in their physical form but which fit the definition of dietary fiber. Together the soluble and insoluble groups make up Total Dietary Fiber.
One reason for thinking of dietary fiber in terms of its soluble and insoluble components has to do with differences in physiological activity. Although the picture is still far from complete and much research remains to be done, certain things appear to be fairly well established. In general, the insoluble components of dietary fiber are associated with decreased gastrointestinal transit times and increased fecal bulk while the soluble components tend to decrease gastric emptying times and influence nutrient absorption. Thus, insoluble components are thought to be associated with a reduced tendency toward bowel disorders. Soluble dietary fiber, on the other hand, is associated primarily with a reduction in low density lipoproteins and serum cholesterol as well as improved glucose tolerance at least in the short term.
In addition, a further advantage of dietary fiber is that a higher intake of dietary fiber may aid in weight reduction through "caloric dilution" and an increased sense of fullness because of bulk. Unfortunately, the benefits of increased fiber intake are not without risks. It is particularly critical to keep in mind that very large amounts of fiber may interfere with the absorption of other nutrients. However, there does not appear to be a problem with modest levels of fiber intake in conjunction with good mineral nutrition. Thus, a proper balance must be found among the types of fiber available to maximize the benefits of fiber at only modest levels of intake.
Because of the complexity of dietary fiber and the difficulty of establishing its effects, no definite recommendations have been set for adequate intake of dietary fiber. It has been estimated that Western diets provide roughly 10-20 grams per day of total dietary fiber. Nutritional experts have suggested that as much as 25-40 grams per day of fiber could be beneficial in the human diet. At the present time, the Canadian Expert Advisory Committee on Dietary Fiber is recommending to increase the intake of dietary fiber to 32 grams per day. Unfortunately, even in view of these seemingly specific recommendations of experts in the field of nutrition, up through the present time no specific recommendations have been promoted as to the preferred types or balance of fiber products.
Many researchers in the field of dietary fiber have recognized in a very general way, the importance of a wide variety of fiber sources in the diet. Because of the differences in types of dietary fiber and because of individual metabolic differences it seems reasonable to obtain fiber from a variety of sources in order to obtain a more balanced intake of all dietary fiber components. However, no composition has yet been formulated which provides an appropriate balance of fiber which takes full advantage of the nutritional aspects of fiber and attempts to develop a balanced formulation. Furthermore, no such fiber composition has been made available which offers not only a balanced formulation but the convenience of unit-of-use administration.